1. Field of the Invention
The invention relates generally to the art of precise position measurement apparatus and systems and more particularly to an improved low cost apparatus and method for generating position-related data such as azimuth and elevation of an object or point within a work area and performing calculations utilizing such data.
2. Description of the Related Art
Precise position measurement data is necessary or useful in a variety of technical fields. Obvious examples include navigation for airplanes and ships which in light of recent technical advances often include navigational aides utilizing global positioning system (GPS) data that may be overlaid on maps to facilitate navigation. Three dimensional position information and data is likewise useful in many other industrial arts including robotic control, virtual reality, augmented reality and particularly the building and construction trades.
Three dimensional positional information gathering apparatus and systems are often costly to deploy in construction type environments and often require highly skilled operators to install and operate the equipment. For example, multiple transmitters might require multiple line of sights and other setup criteria that can only be obtained using large and expensive equipment which is often not well adapted to field use. ArcSecond of Dulles, Va. manufactures and sells the improved low cost precision 3D system described in the Hedges et al. U.S. patent applications identified above. The ArcSecond Falcon system is one of the simplest and most user friendly precision 3D measurement systems and employs at least two optical transmitters, one or more selectively positionable optical receivers and sophisticated algorithms for calculating 3D data within the predetermined work area.
As will be well known to those skilled in the construction and building trades, many commercially significant tasks require precise position measurement information or data but generally do not require three dimensional data. For example, leveling a floor in the building trade requires only elevation data (one dimension), turning an angle from a comer location to mark the position of a wall requires azimuth data in a plane (two dimensions). Similarly a myriad of other such applications in the building and construction trades can be performed with combinations of elevation and azimuth data relating to a particular task. Thus a precise position measurement system that provides two dimensional data would have many practical commercial building and construction applications. However as with the 3D position measurement systems, two dimensional position measurement systems in the past have not been adapted for efficient field use. Additionally, prior art two dimensional measurement systems generally required two or more operators and were difficult to set up and maintain for field operation. Thus there has been, in applicants"" opinion, a long felt need for an improved low cost spatial positioning system capable of generating precise two dimensional information and which is well adapted to efficient field setup and use.
Accordingly it is an object of the present invention to provide an improved low cost 2D position measurement apparatus and process which is both easy to set up in the field and capable of single operator utilization.
It is another object of the present invention to provide improved 2D measurement apparatus and process which is precise, rugged, reliable and easy to set up and used by a single operator under construction site conditions.
It is a further object of the present invention to provide an improved low cost robotic theodolite system and procedure for conveniently generating azimuth and elevation angle data based upon detected timing differences between illuminating laser beam strikes and a reference strobe and based upon convenient calibration data for the utilized optical transmitter.
Novel features of applicants"" invention are directed to overcoming the above described deficiency in prior art precision position measurement systems by providing novel system apparatus and processes for: (i) calculating elevation angles based upon laser fan beam strikes or hits as a single rotatably mounted transmitter emits two constant laser beams from a rotating head, where selected parameters of the rotating fan beams have been precisely determined during a calibration procedure associated with the manufacture of said transmitter, and a receiver which uses a single light responsive element, (ii) further calculating azimuth angles using a single periodic reference pulse from a series of light emitting diodes, (LEDs) the reference pulse preferably generated once per revolution of the transmitter rotating head and the reference pulse being received by the same single light responsive element. In another embodiment of the present invention the improved system and process can be adapted to make distance calculations by using two receiver elements, which are positioned in the measurement field at a known distance separation, and which receive only the two rotating laser beams and the reference pulse.